1. Technical Field
The present invention relates, in general, to a circular filtering disc and a filter device having the filtering disc and, more particularly, to a circular filtering disc and a filter device having the filtering disc, in which raw water is supplied to the filter device through the circumferential edges of a plurality of circular filtering discs stacked on top of one another in the filter device and is filtered prior to being discharged from the filter device through the center of the filtering discs.
2. Description of the Related Art
Generally, to produce drinking water from the raw water of a natural spring, the raw water must be subjected to several processes for removing sludge from the water and for purifying the water. Further, to supply water to a public swimming pool or to recycle the water of the swimming pool, it is required to completely remove even fine sludge from the water.
A conventional filter device used for executing the water filtering processes includes a plurality of filtering discs having a rectangular shape, which are stacked on top of one another in the filter device, as shown in FIG. 1.
Each of the conventional filtering discs 10 includes a vertical inlet hole 14, which is vertically formed through the disc 10 in an edge of the disc 10 and supplies raw water to the filter device, and a vertical outlet hole 15, which is vertically formed through the disc 10 in another edge of the disc 10 and discharges filtered pure water from the filter device to the exterior. A middle plate 11 horizontally lies in a middle portion between the vertical inlet hole 14 and the vertical outlet hole 15. The middle plate 11 is provided with a plurality of partitions on each of upper and lower surfaces thereof, thus forming a plurality of upper and lower channels 12 and 12a at locations between the partitions. Placed on the upper channels 12 is a filter fabric 13.
A radial inlet hole 14a is formed in the filtering disc 10 such that the upper channels 12 communicate with the vertical inlet hole 14 by way of the radial inlet hole 14a. In the same manner, a radial outlet hole 15a is formed in the filtering disc 10 such that the lower channels 12a communicate with the vertical outlet hole 15 by way of the radial outlet hole 15a. 
To fabricate a filter device, a plurality of filtering discs 10 having the above-mentioned structure are stacked on top of one another and, thereafter, the filtering discs 10 are tightened together using upper and lower end plates placed on the top and bottom of the discs 10. Raw water is supplied to the filter device through the vertical inlet holes 14 of the filtering discs 10 and is filtered by the discs 10 prior to being discharged from the filter device to the exterior.
Here, to improve the filtering efficiency of the filter device, a filter medium, such as active carbon, is applied to the filter fabrics 13. To apply the filter medium to the filter fabrics 13 prior to executing a filtering operation, the filter medium, such as the active carbon, is added to raw water and is supplied along with the raw water to the filtering disc through the vertical inlet holes 14 such that the active carbon can be applied to the lower surfaces of the filter fabrics 13, thus being coated thereon to a predetermined thickness.
After completing the application of the filter medium to the filter fabrics 13, raw water to be filtered is applied to the filtering disc through the vertical inlet holes 14 and is filtered by the filter fabrics 13 while the raw water passes through the filter fabrics 13 placed below the respective filtering discs 10. Filtered pure water is discharged from the filter device to the atmosphere through the vertical outlet holes 15.
However, because the conventional filtering disc has a rectangular shape, raw water is supplied to the filtering disc through only the left edge and filtered pure water is discharged from the filtering disc through only the right edge (of course, although pure water may be supplied to the disc through the front edge and pure water may be discharged through the rear edge, the water inlet and outlet edges of the disc are referred to as left and right edges based on FIG. 1), so that water pressure concentrically acts on the left and right edges of the filtering disc.
Therefore, water resistance acting on the filtering disc is not evenly distributed on the entire surface of the filtering disc, but is concentrically distributed on the left and right edges of the filtering disc, thus reducing the filtering efficiency. Further, because water pressure concentrically acts on the edges of the filtering disc, when the filtering disc receives an impact at the edges it may break.
Further, the filter fabrics are partially contaminated at the edges, so that the filtering discs must be frequently replaced by new ones, thus increasing the maintenance cost of the filter device.